How much energy would a jeweler need to melt 4.4 g of copper to fix a broken necklace if the copper starts out at 25°c and melts at 1083°c

1792 J.

Explanation:

The amount of heat released from Cu = Q = m.c.ΔT.

where, m is the mass of Cu (m = 4.4 g).

c is the specific heat capacity of Cu = 0.385 J/g°C.

ΔT is the temperature difference = (final T - initial T = 1083°C - 25°C = 1058°C).

∴ The amount of heat released from Cu = Q = m.c.ΔT = (4.4 g)(0.385 J/g°C)(1058°C) = 1792 J.

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation: